NUTRITION. 33 



monly applied to that part of a plant which is 

 beneath the earth, but this is not an exact defi- 

 nition, as there are roots which exist out of the 

 soil altogether,* it may be more correctly de- 

 scribed as that portion which vegetates down- 

 wards. The point of junction between the stem 

 and the root bears the name of the neck, or 

 crown : from this point they proceed in oppo- 

 site directions, so that the part the nearest to 

 this is, in both organs, the oldest, and in gene- 

 ral the thickest. The office of the root is 

 double, it both serves to fix the plant in the soil, 

 and to imbibe its requisite nourishment. Roots 

 are never green excepting at their extremity where 

 it has been shown (8) that they perform their 

 function of absorbing water through their spon- 

 gioles. As soon as a plant begins to exist, a 

 principal, or tap root, may always be perceived, 

 growing in an opposite direction to the stem : 



* Such are the curious braces as they may be called 

 sent out by the Pandanus, or Screw Pine this stem is' 

 smaller at the bottom than it is above, and ae this form 

 is of course unfavourable to the steadiness of tlie plant 

 in the ground, it sends out roots at various distances up 

 the stein which find their way into the earth, and thus 

 act as buttresses for its support. Such is also the well 

 known method by which the Banyan, from a single tree 

 becomes a grove. 



